I think the problem ocours only, if you once switched to ‘manual Network selection’.
Once you did that, the phone stops connecting automatically to a Network, even when you switch the toggle-switch back to ‘automatic’.
The solution is in this thread, you have to resett the ANS settings.
From my point of view, there is a glich in the software with the toggle-switch.
Traveling in Spain as well, I can confirm @Hifox : Choosing networks automatically worked perfectly until on the ferry I decided to pick one network manually to not get that very expensive satellite network from the ship.
Back on the island I set it back to automatic but whenever I was out of reach of the provider I had selected on the ferry, I would get notficiations about lost network frequently, sometimes every few seconds. They also ignored the do not disturb mode…
Resetting the provider settings helped
Well the first problem in my eyes is that automatic selection does not work and you have to manually select at all. Then the second issue kicks in
Hello,
To be precise: in my experience automatic network selection does work out of the box or after reset of mobile settings. Fairphone 5 will connect to whichever partner networks it finds.
It’s only when one clicks the ANS setting, to actively connect to a different network or even just to check whether it works one cannot get ANS back to work, only by resetting mobile settings.
Regards,
Fairflix
Well above are several reports about ANS not working and therefore network had to be selected manually which then showed the second issue.
This is exactly what it is 
Supposed to be fixed with the update today: Software update: FP5.UT2E.B.078.20241105 and FP4 A.13 MR9/FP4.TP2N.C.0128
Smooth update for me; didn’t yet have time to check if the automatic network selection was fixed.
Just tried to select a network and go back to automatic. I don’t like the UX, but it works.
I don’t know about the constant messages of network failure, that’s too much effort to test